A driving device includes an output voltage decomposing unit which decomposes an output voltage applied to an ultrasonic transducer into a basic and harmonic components; an output current decomposing unit which decomposes an output current flowing through the ultrasonic transducer into a basic and harmonic components; a capacitor current calculator which calculates a basic and harmonic components of a capacitor current, based on the basic and harmonic components of the output voltage; a driving current calculator which calculates a basic and harmonic components of a driving current based on the basic and harmonic components of the output current and the capacitor current, a driving current summing unit which sums up the basic and harmonic components of the driving current, and a constant current controller which generates constant current control data.